SymTech Laboratories wrote:At ~310Hz (18,600 RPM) and 50% DC, the temperature rise over a thirty minute period was approximately 10.0°C. At 85% DC, the temperature rise was about 14.5°C. The measured temperature rise is consistent with the DPAK part's junction-to-ambient thermal resistance and total power dissipation at that frequency and duty cycle.

A quick note about the test conditions: the readings were taken from bare parts on a paper substrate (no copper, no heatsinks). The VND5N07 was covered to minimize air flow over it.

So from these test, I don't see how any normal operating conditions could ever be problematic, at least from a heat generation point of view. From your description, you have use an absolute worst case scenario in terms of dissipating the heat from the VND5N07.

I assume it would be possible to find other injectors that would generate more flyback energy or more steady state current but even if it were to double the generated heat (which would be unlikely) it would still not be enough to create an issue.

So there is a need to find some abnormal conditions that could create the observed failures. Or it is a manufacturing or QA issue and some substandard parts are getting through. Or assembly is damaging the part somehow. Or am I missing something?

racingmini_mtl wrote:So there is a need to find some abnormal conditions that could create the observed failures. Or it is a manufacturing or QA issue and some substandard parts are getting through. Or assembly is damaging the part somehow. Or am I missing something?

Your summary is accurate. Barring manufacturing issues, it definitely seems as though there are either extraordinary conditions in the field or defective parts. We're still in communication with ST to rule out defective parts.

It might be helpful if anyone with a faulty VND5N07 posts the date/sequence code etched on the surface of the chip (e.g. "GK0HL132").

Just a question, how to quickly solve a problem when one has a defective VND on a MS3X board. Is it possible to replace them all with the injector driver transistors that are used on the MS mainboard? For example using 8 such transistors and reviring them to some heat sink or directly on the case. I used them for years on plain MS1/MS2 driving 6 injectors on a single transistor and never had a problem. To me they seem very robust compared to the VND chips.

mega_user wrote:Just a question, how to quickly solve a problem when one has a defective VND on a MS3X board. Is it possible to replace them all with the injector driver transistors that are used on the MS mainboard? For example using 8 such transistors and reviring them to some heat sink or directly on the case. I used them for years on plain MS1/MS2 driving 6 injectors on a single transistor and never had a problem. To me they seem very robust compared to the VND chips.

A reply would be much appreciated.

The mainboard transistors require an interface IC; they can't be driven directly from the MS3

mega_user wrote:Just a question, how to quickly solve a problem when one has a defective VND on a MS3X board. Is it possible to replace them all with the injector driver transistors that are used on the MS mainboard? For example using 8 such transistors and reviring them to some heat sink or directly on the case. I used them for years on plain MS1/MS2 driving 6 injectors on a single transistor and never had a problem. To me they seem very robust compared to the VND chips.

A reply would be much appreciated.

We don't mean to contradict Peter, but you could probably drive a IRFIZ34N directly from the processor with a large enough gate resistor (510 ohm - 1k ohm). The total gate charge of an IRFIZ34N is a little greater than the gate charge of the VND5N07, but as long as you don't try PWM current limiting (kHz range switching frequency), the FET should switch fast enough for driving high impedance fuel injectors or low impedance injectors with inline resistors (~6.8uS @ 5mA).

You would have to be sure to use a genuine IRFIZ34N, which is avalanche rated, unless you also want to duplicate the active flyback clamp circuit. Of course, without the MOSFET driver IC, PWM current limiting is totally out of the question, so you wouldn't need the PWM flyback damping circuit.

This wouldn't be an ideal situation, but it could work as a quick fix.

Only using regular hi impendance injectors. No PWM current limiting. Will the MS3X board support the IRFIZ34 instead of the VND without doing some damage to the board or the processor? Looking at the V2.2 board ouput section there is a MC34151P between the processor and the IRFIZ injector drivers. So it can be done with only a resistor in between?

Can you also write down some simple instructions how to revire the MS3X board? Which pin from the VND goes to which pin on the IRFIZ?

As said I'm looking for a quick and a simple fix. While the VND problem is being worked on.

mega_user wrote:Just a question, how to quickly solve a problem when one has a defective VND on a MS3X board. Is it possible to replace them all with the injector driver transistors that are used on the MS mainboard? For example using 8 such transistors and reviring them to some heat sink or directly on the case. I used them for years on plain MS1/MS2 driving 6 injectors on a single transistor and never had a problem. To me they seem very robust compared to the VND chips.

A reply would be much appreciated.

We don't mean to contradict Peter, but you could probably drive a IRFIZ34N directly from the processor with a large enough gate resistor (510 ohm - 1k ohm). The total gate charge of an IRFIZ34N is a little greater than the gate charge of the VND5N07, but as long as you don't try PWM current limiting (kHz range switching frequency), the FET should switch fast enough for driving high impedance fuel injectors or low impedance injectors with inline resistors (~6.8uS @ 5mA).

You would have to be sure to use a genuine IRFIZ34N, which is avalanche rated, unless you also want to duplicate the active flyback clamp circuit. Of course, without the MOSFET driver IC, PWM current limiting is totally out of the question, so you wouldn't need the PWM flyback damping circuit.

This wouldn't be an ideal situation, but it could work as a quick fix.

Actually, I don't mean to contradict you but the IRFIZ34N is not a logic-level FET. So that would _not_ be a good idea to use it this way. You'd need to use the IRLZ34N since this is the logic-level equivalent.

And note that while this is fully avalanche rated, the single pulse avalanche rating is about half of what the VND5N07 is rated for. So I don't know if that would be a better solution than the original MS3X drivers. Of course, you can more easily use a better heat sink (such as the case) with that package.

racingmini_mtl wrote:Actually, I don't mean to contradict you but the IRFIZ34N is not a logic-level FET. So that would _not_ be a good idea to use it this way. You'd need to use the IRLZ34N since this is the logic-level equivalent.

And note that while this is fully avalanche rated, the single pulse avalanche rating is about half of what the VND5N07 is rated for. So I don't know if that would be a better solution than the original MS3X drivers. Of course, you can more easily use a better heat sink (such as the case) with that package.

We spoke too soon, you're absolutely correct. 5V isn't sufficient to turn on the IRFIZ34N, so he would need an IRLZ34N or comparable logic level MOSFET. In addition to the decreased avalanche rating, it doesn't seem like heat is a big factor in these few VND5N07 failures anyway. So there's isn't really a good reason to try to use IRxxZ34N MOSFET's at all.

I was told by Bruce years ago that the FET driver was needed to insure enough gate drive.Having said that, it should be noted that the on board FET's are designed to drive low impedance loads, even throttle body injectorsThe fets might work with logic drive but you might find that some devices don't work or it doesn't work under all conditions,

Peter Florance wrote:I was told by Bruce years ago that the FET driver was needed to insure enough gate drive.Having said that, it should be noted that the on board FET's are designed to drive low impedance loads, even throttle body injectorsThe fets might work with logic drive but you might find that some devices don't work or it doesn't work under all conditions,

At high speeds, the VND5N07 would need a driver too. If you're not using PWM current limiting, and you can provide enough voltage to the gate, a driver isn't strictly necessary; you're just limited by the amount of current the microcontroller pin can source while the FET is switching, so it will switch a little slower (i.e. in a few microseconds instead of nanoseconds). With PWM current limiting disabled, the FET will only be switching at a couple of hundred Hertz maximum, so a ~6uS rise time is acceptable. At 17kHz, ~6uS is much too much.

SymTech Laboratories wrote:At high speeds, the VND5N07 would need a driver too.

I thought these were not strictly FET's but haven't looked that closely at the specs. So the input pin is tied to a gate? That would make sense that CPU can't source enough current to charge the gate at full speed.

Edit: when I say full speed, I mean device's potential, not our fairly slow speed application.

Peter Florance wrote:I thought these were not strictly FET's but haven't looked that closely at the specs. So the input pin is tied to a gate? That would make sense that CPU can't source enough current to charge the gate at full speed.

Edit: when I say full speed, I mean device's potential, not our fairly slow speed application.

That's correct, the input is tied directly to the gate under normal conditions. If the part overheats, the input will be disconnected from the gate and connected to ground through a 100R resistor instead.

mega_user wrote:Then it is not a good idea to use the main board injector drivers? What if one replicates the main board circuit from the processor to the injector drivers?

You must replicate the whole circuit, including R14, R15, R17, R20, D3, D17, D18, D21, C13, C14, the MOSFET driver IC (U4), and the MOSFET's (Q1 and Q5). You could omit the other parts as long as you're using high impedance injectors and Avalanche rated MOSFET's.

Whe are building a ms 3 on a bmw 2002. What can whe do ? Take the risk ?Use the mainboard drivers? Use the msx3 whit the zenerdiodes , the schotty diodes .?Whe do not want it to fail in a expensive rally.

Just to let you all know that "behind the scenes" this is being taken seriously and investigated in a methodical manner. Everything that can be done is being done.

Analysis of the datasheet suggests that the circuit is fine and the devices are being used as the manufacturer intended.

While any component failure is a problem, do remember that there are hundreds of engines out there running with these devices.From what I gather, _most_ reported failures have been "dead on arrival" so once you are up and running the failure rate is very low.

Personally I have no plans to do anything different with the VNDs on my MS3 ECUs.

First post and a sad tale, bummerI think I have a dead vnd5n07 on my microsquirt 2.2 board. It's only ever run up on a stimulator. It's getting a signal from cpu but does not conduct other ign channel is fineAny suggestions on repair and replacement? I have no smd rework equipment.Any further news on the reason for failure ? as it seems mine was a DOA but you can't always be sure.